1. Field of the Invention
This invention relates to a transdermal absorptive drug formulation containing 3-isobutyryl-2isopropylpyrazolo-[1,5-a ]pyridine ( hereinafter referred to as ibudilast according to its international nonproprietary name) which is an improving drug for bronchial asthma and cerebrovascular disorder.
2. Description of the Related Art
Ibudilast is well known as a chemical compound developed by Irikura et al. (Japanese Patent Publication Sho 52-29318, corresponding to U.S. Pat. No. 3,850,941, U.K. Patent 1,378,375 and so on) and has been proved by clinical tests to be useful for preventing and treating bronchial asthma, and still more its utility as an improved drug for cerebrovascular disorder has been reported. When the ibudilast is orally administered to human in a dosage form having no substantial release, a rapid absorption from alimentary tract will produce a steep rise of serum concentration, resulting in side-effects such as nausea and vomitting. Therefore, as far as oral drugs are concerned, sustained release capsules, tablets and the like are proposed for the compound (Japanese Laid-Open Patent Application Sho 60-193913, corresponding to EP-A-0 156 243). Also the compound has been successfully prepared for rectal administration because of finding out bases for preventing a rapid increase in the serum concentration (Japanese Laid-Open Patent Application Sho 60-193913).
Since bronchial asthma and cerebrovascular disorder are often found among children and senile patients, respectively, it has been strongly desired that the development of a dosage form of ibudilast which is more easily administered.